Simulation of the movement of rice grains in a centrifugal huller by discrete element method and the influence of blade shape

Abstract

Problems of low one-time hulling ratio and high grain breakage can occur during rice processing. Understanding the interaction mechanism between grains and blade in a centrifugal huller is the key to improving its performance. In this study, the discrete element method was used to simulate the movement of rice in centrifugal huller. The feasibility of simulation and particle modelling was confirmed by experiments. The results showed that some grains can lack the necessary acceleration, which can lead to the velocity difference between grains. With increasing radial position, the orientation angle of grains gradually changed to angles that were not conducive to hulling. The friction work done by the blade to the grains causes reductions in the rotational kinetic energy of the grains. When the grains are located alongside the upper or the lower layers of the huller wall, the proportion of grains moving at their optimal hulling angle is greater and the long axis of grain tends to be adjusted to become parallel to the baffle. Based on the principle of minimising the rebound of grains on the blades and reducing the rotational kinetic energy of grains themselves, a new type of V-shaped concave blade was investigated. Compared with original blade, the hulling ratio was increased by 8% and breakage ratio was decreased by 7.33% using the concave blade. This study can provide theoretical guidance for the design of centrifugal huller or similar grain processing equipment.